When a test tube containing a blood sample arrives at a laboratory where tests are to be performed on the sample, it must be determined whether there is a large enough sample to conduct the ordered tests. More specifically, after the sample is separated in a centrifuge, it is necessary to determine the amount of red blood cells and serum or plasma, in the sample.
Sometimes, organic separation gel is added into the tube in order to store the sample. The gel provides a hydrophobic barrier between the serum and the red blood cells and thereby prevents the red blood cells from metabolizing the components of the serum. Therefore, it is also necessary to determine if gel is present in the sample.
These tasks are traditionally performed by visual inspection. However, generally, before the test tube arrives at the laboratory, many labels are placed on the test tube. Several layers of labels make visual inspection very time consuming and difficult, if not impossible. Accordingly, there is a need to easily, quickly, inexpensively, reliably, and safely determine if there is a large enough sample present in a test tube that is covered in labels to conduct required tests.
The present invention meets this need by providing a method for detecting interfaces in a container made up of a material and having a vertical axis and containing an upper layer of serum or plasma and a lower layer of cells. The container can also contain a middle layer of gel and have a cap. The container can be a test tube made up of plastic or glass.
A first detecting light beam, which is substantially transmitted by serum, plasma, labels and the material but substantially blocked by the cells, is projected onto the container. A portion of the first detecting light beam is transmitted through the container. A second detecting light beam, which is substantially blocked by serum, plasma, and cells, but substantially transmitted by the material and labels, is also projected onto the container. A portion of the second detecting light beam is transmitted through the container. Lasers, either directly or through fiber optic cables, can project the light beams.
Then, the portion of the first detecting light beam that is transmitted through the container and no significant portion of the second detecting light beam is detected as a function of position along the vertical axis of the container. Likewise, the portion of the second detecting light beam that is transmitted through the container and no significant portion of the first detecting light beam is detected as a function of position along the vertical axis of the container. Then, the location of interfaces is determined from the detected portions.
The first and second detecting light beams can be projected by respective projectors, and detected by respective detectors. The light beams preferably are substantially perpendicular to the longitudinal axis of the container, and can be coplanar.
The present invention further provides an apparatus for detecting the location of at least one interface in a container made up of a material and having a vertical axis and containing an upper layer of serum or plasma and a lower layer of cells. A first projector projects onto the container a first detecting light beam that is substantially transmitted by serum and plasma and the material but is substantially blocked by the cells. A portion of the first detecting light beam is transmitted through the container. A second projector projects onto the container a second detecting light beam that is substantially blocked by serum, plasma, and cells, but is substantially transmitted by the material. A portion of the second detecting light beam is transmitted through the container.
A first detector detects, as a function of position along the vertical axis of the container, the portion of the first detecting light beam that is transmitted through the container. A second detector detects, as a function of position along the vertical axis of the container, the portion of the second detecting light beam that is transmitted through the container. A processor is operably attached to the detectors and determines the location of interfaces from the detected portions.